Process for Lobe and Journal Preparation and Weld Repair

ABSTRACT

A process for repairing a section of a rotatable shaft is disclosed. The section of the rotatable shaft has a surface portion having a surface parallel to an axis of rotation of the rotatable shaft and axial ends perpendicular to the axis of rotation of the rotatable shaft. The process includes preparing a well region extending over a perimeter of the section and extending downward in the surface portion, depositing material into the well region to fill the well region using a welding process and displacing a portion of the material that was deposited in the well region. The well region has a bottom portion that is substantially parallel to the axis of rotation and includes opposing sidewalls. Each sidewall extends proximate to the axial ends of the rotatable shaft and directly adjoins a remaining portion of the surface portion.

TECHNICAL FIELD

The disclosure generally relates to a process for repairing a section ofa rotatable shaft, and more particularly to a process of repairing asection of a rotatable shaft, such as a lobe or a journal utilizingwelding processes.

BACKGROUND

Rotatable shafts having eccentric features formed on portions of theirouter surfaces are commonly used in various machines requiringcyclically timed mechanical events or actuations of various components.For example, an internal combustion engine may use a rotating camshaftfor timed actuation of intake or exhaust valves controlling the flow ofair and exhaust into and out from one or more combustion chambers.Camshafts are typically unitary structures having lobes or eccentricfeatures protruding therefrom. The lobes are arranged to periodicallypush a roller or follower connected to another engine component, wherethe roller or follower tracks an outer periphery or race of each lobe.

In a typical camshaft application, each lobe is typically continuouslyin contact with a roller or follower. The interface between the cam lobeand follower is subject to compressive forces and friction, causing wearand/or damage to the lobe during prolonged use, or when a defectivecondition is present. For example, in instances where inadequatelubrication of the interface is provided and/or situations when thefollower is not properly aligned with its respective lobe, wear and/ordamage to the lobe may occur. Prolonged extensive use will result inwear as well. A damaged and/or worn lobe may directly affect the motionof the follower and, hence, operation of the engine. Therefore, it isnecessary to either replace or rebuild the camshaft.

One of the challenges associated with rebuilding camshafts is rebuildingthe eccentric features, such as lobes and journals, on the shaft. Theseeccentric features commonly have portions that stand proud of the minordiameter of the feature creating raised, square-edged, stepped profiles.It is difficult to efficiently rebuild these features and, in particularto rebuild the square-edge original to the feature due to weldingdynamics and weld bead surface tension. Economic considerations,however, dictate that it is usually more desirable to rebuild a worncamshaft instead of replacing the worn camshaft with a new one.

Different welding strategies have been employed to repair the wornportions of rotatable shafts and address issues associated with therepair such as downtime and material costs. For example, U.S. Pat. No.5,172,475 (“Amos et al.”) issued Dec. 22, 1992 discloses a prior artmethod for repairing a rotor that entails severing the rotor into two ormore segments, removing the crack from the rotor and depositing weldmaterial onto the rotor until the removed portion is replaced with weldmetal. Additional welding is performed to build up enough stock tomachine a welding preparation, which is used to provide a surface toweld together the rotor body 14 and the stub end 18. See Col. 2, lines24-55, and FIGS. 1 and 2.

While prior art methods of repairing worn rotatable shafts are useful tosome extent, these methods do not specifically address the difficultiesassociated with welding eccentric features such as lobes and journals.Therefore, there remains a need to more efficiently repair rotatableshafts, including features such as lobes and journals while maintainingthe square edge original to the feature. Accordingly, the disclosedprocess for repairing a section of a rotatable shaft is directed atovercoming one or more of these disadvantages in currently availablerepair methods.

SUMMARY

In accordance with one aspect of the disclosure, a process for repairinga section of a rotatable shaft is disclosed. The section of therotatable shaft includes a surface portion having a surface parallel toan axis of rotation of the rotatable shaft. The section of the rotatableshaft further includes axial ends perpendicular to the axis of rotationof the rotatable shaft. The process includes preparing a well regionextending over a perimeter of the section and extending downward in thesurface portion. The well region has a bottom portion that issubstantially parallel to the axis of rotation and includes opposingsidewalls. Each sidewall extends proximate to the axial ends of thesection and directly adjoins a remaining portion of the surface portion.The process further includes depositing material into the well region tofill the well region using a welding process and displacing a portion ofthe material that was deposited in the well region.

In accordance with another aspect of the disclosure, a process ofrepairing a section of a rotatable shaft is disclosed. The sectionextends eccentrically from the rotatable shaft and includes a surfaceportion having a surface parallel to an axis of rotation of therotatable shaft. The section also includes axial ends perpendicular tothe axis of rotation of the rotatable shaft. The process includesmilling a well region extending over a perimeter of the section andextending downward in the surface portion. The well region has a bottomportion that is substantially parallel to the axis of rotation andincludes opposing sidewalls. Each sidewall extends proximate to theaxial ends of the section and directly adjoins a remaining portion ofthe surface portion. The process further includes depositing materialinto the well region to fill the well region by using laser clad weldingand grinding a portion of the material that was deposited in the wellregion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of thisdisclosure, and the manner of attaining them, will become apparent andbe better understood by reference to the following description of oneaspect of the disclosure in conjunction with the accompanying drawings,wherein:

FIG. 1 is a front plan view of a section of a rotatable shaft that mayutilize the process according to an aspect of the disclosure.

FIG. 2 is a flowchart of the process of repairing a section of arotatable shaft according to an aspect of the disclosure.

FIG. 3 is a front plan view of the section of the rotatable shaft shownin FIG. 1 after the well region is prepared according to an aspect ofthe disclosure.

FIG. 4 is a partial cross-section view of the section shown in FIG. 3cut along the axis of rotation according to an aspect of the disclosure.

FIG. 5 is a graphical representation of the process of repairing asection of the rotatable shaft according to an aspect of the disclosure.

FIG. 6 is a combustion engine having components that may be repairedutilizing aspect of the disclosure.

DETAILED DESCRIPTION

FIG. 1 is a front plan view of a section of a rotatable shaft that mayutilize the process according to an aspect of the disclosure. Referringto FIG. 1, a section 10 of the rotatable shaft 20 is shown. Therotatable shaft 20 may be an elongated member, such as, for example, acamshaft. The rotatable shaft 20 has an axis of rotation A and isconfigured to rotate three-hundred and sixty degrees (360 degrees)around the axis of rotation A. The rotatable shaft 20 may be driven torotate, such as, for example, by a camshaft drive, chain, or othersuitable means.

The rotatable shaft 20 includes a section 10, which rotates assubstantially one body with the rotatable shaft 20. The section 10 is,for example, affixed to or integral with the rotatable shaft 20. Thesection 10 includes a surface portion 30 with a surface that may beparallel to the axis of rotation A. The section 10 further may includeaxial ends 40 that are perpendicular to the axis of rotation A of therotatable shaft 20.

The section 10 of the rotatable shaft 20 has a generally circularcross-section. The circular cross-section of the section 10, however,may be non-uniform. In some aspects, the section 10 is eccentric (i.e.,non-concentric) relative to the axis of rotation A of the rotatableshaft 20. The profile of the section 10 depends on the particularapplication of the section 10 and the rotatable shaft 20.

In some aspects, the section 10 is a lobe for a rotatable shaft 20, suchas a camshaft for an engine. In other aspects, the section 10 is ajournal or other type of bearing for a rotatable shaft 20. The section10 and the rotatable shaft 20 are composed of materials such as castiron, cast steel, forged steel, aluminum or other materials suitable fortheir application.

During operation of the rotatable shaft 20, the section 10 may sufferwear and/or become damaged. For example, wear or damage may occur insituations when inadequate lubrication, misalignment, or another failureoccurs that affects the working interface between the section andanother component or in general, any follower component contacting thesection. Excessive operation may result in a worn section 10 as well.Such conditions can require replacement and scrapping of the rotatableshaft 20. The rotatable shaft 20, however, may advantageously berepaired by the disclosed process as described below.

The disclosure provides various aspects for a process associated withrepairing a section 10 of a rotatable shaft 20 that is worn or damagedto avoid scrapping the rotatable shaft 20 in favor of a new one. FIG. 2illustrates a flowchart of a process 100 for repairing a section 10 of arotatable shaft 20 according to one aspect of the disclosure. At process110, a well region 50 is prepared in the worn section 10. A millingprocess may be employed to prepare the well region 50. The millingprocess may be performed using a key slot cutter or a ball nose endmill. Alternatively, the well region 50 may be prepared using a grindingprocess or a machining process. Preparing the well region 50 requiresremoving at least the worn or damaged portion of the section 10 of therotatable shaft 20. Additional material, however, may be removed fromthe section 10 during process 110. Once process 110 is completed, therepair process 100 may optionally proceed to process 120 (pre-weld heattreatment) as explained below. Alternatively, after process 110, theprocess 100 may omit process 120 and proceed to process 130 (depositingmaterial in the well region 50) after process 110 is completed.

Referring now to FIG. 3, a portion of the section 10 of the rotatableshaft 20 is shown after the well region 50 has been prepared in process110. FIG. 4 illustrates a partial cross-section view of the section 10shown in FIG. 3 cut along the axis of rotation A. As shown, the wellregion 50 extends downward into the surface portion 30 and extendsthroughout the perimeter of the section 10. The well region 50 has abottom portion 60 and opposing sidewalls 70. The bottom portion 60 maybe substantially parallel to the axis of rotation A. Each sidewall 70extends proximate to the axial ends 40 and directly adjoins a remainingportion of the surface portion 30. In some aspects, fillets 80 may beformed between the bottom portion 60 and the sidewalls 70 to reducestrain. The well region 50 may have geometries differing from the oneshown in FIGS. 3 and 4. For example, the bottom portion 60 and thesidewalls 70 may be curved such that the well region 50 is curved. Forexample, the well region 50 may have a curved bottom portion 60 andcurved sidewalls 70. The well region 50 may also have sidewalls 70 thatare angled.

At 120, the section 10 may be pre-weld heat treated to prepare the wellregion 50 and the section 10 for subsequent processes in the repairprocess 100. This pre-weld heat treatment occurs after preparing thewell region 50 in the section 10 (process 110) and prior to depositingmaterial into the well region 50 (process 130). The pre-weld heattreatment occurs at a high temperature for a specified period of time toensure that the surface of the well region 50 is adequately prepared fordepositing material in the well region 50. This pre-weld heat treatmentprocess 120 is optional and depends on the welding process used inprocess 130, and the type of material deposited into the well region 50as well as the material of the section 10 and the specific applicationof the section 10. Pre-weld heat treatment prior to welding may achievebetter weld penetration and slow the cooling process after welding toallow for added stress relief, reduced material hardening and the like.Once process 120 is completed, the repair process 100 proceeds toprocess 130 (depositing material into the well region 50) as explainedbelow. In lieu of process 120 or in addition to process 120, the wellregion may be cleaned and prepared for the next process. This processmay include sanding, sandblasting, grease removal, grinding, coatingremoval, and the like.

At process 130 of the repair process 100, material is deposited into thewell region 50 to fill the well region 50. The material deposited inprocess 130 replaces the material that was removed from the section 10when the well region 50 was prepared in process 110. In general, theamount of material deposited in process 130 may be greater than theamount of material that was removed from the section 10 in process 110to prepare the well region 50. The material deposited in process 130 maybe the same or similar to the material that the section 10 is composedof and includes materials such as iron, steel, aluminum, stainlesssteel, titanium, nickel or other suitable materials for a section 10 ofa rotatable shaft 20. The material deposited may also includetitanium-based alloys, nickel-based alloys such as Inconel® and otheralloys. Powder or wire feedstock may be used as the source of materialto be deposited. In some aspects according to the disclosure, steelpowder or steel wire is used as feedstock for the material deposited.

Process 130 may be carried out using at least one of the followingwelding processes: Laser Beam (LB) Welding, Plasma Transfer Arc (PTA)Welding, Electron Beam (EB) Welding, Metal Inert Gas (MIG) Welding,Tungsten Inert Gas (TIG) Welding, or any other suitable weldingprocesses. These welding processes can be carried out under an inert gasatmosphere, with inert gas shielding, or under vacuum to preventexcessive oxidation. For example, argon, carbon dioxide, helium gas orthe like may be provided with some of aforementioned welding processes.In one aspect according to the disclosure, Laser Beam (LB) Welding isused in process 130 to deposit material into the well region 50. In yetanother aspect, argon gas is used with Laser Beam (LB) Welding inprocess 130 to deposit material into the well region 50. Laser Beam (LB)Welding, however, may be performed with other protective gases such ascarbon dioxide or helium. Of course, process 130 may be implementedwithout any specialized inert gas atmosphere.

Process 130 may be performed using multiple consecutive passes asnecessary to fill the well region 50 with deposited material. Onceprocess 130 has been completed, the repair process 100 may optionallyproceed to process 140 (post-weld heat treatment) as explained below.Alternatively, the repair process 100 may omit process 140 and directlyproceed to process 150 (displacing a portion of the deposited material)after process 130 is completed.

At process 140, the section 10 of the rotatable shaft 20 may bepost-weld heat treated to relieve stress or the like. This post-weldheat treatment process 140 occurs after depositing material in the wellregion 50 (process 130) and prior to displacing a portion of thedeposited material (process 150). The post-weld heat treatment process140 is similar to a post-weld heat treatment that is well known to thoseskilled in the art. In the post-weld heat treatment process 140, thesection 10 of the rotatable shaft 20 is typically heated at a hightemperature for a specified period of time. This post-weld heattreatment process 140 is optional but in some instances maysubstantially reduce the risk that the section 10 and the rotatableshaft 20 will crack after welding. The post-weld heat treatment may havesome other benefits as well. In some instances, this post-weld heattreatment process 140 depends on the welding process used in process130, the specific application of section 10, and the type of materialdeposited into the well region 50. Once process 140 is completed, therepair process 100 proceeds to process 150 (displacing a portion of thedeposited material) as explained below.

At process 150 of the repair process 100, a portion of the materialdeposited in the well region 50 is displaced. A grinding process can beused to displace a portion of the material deposited. Alternatively, amilling or machining process may be used to displace a portion of thematerial deposited in the well region 50. Process 150 is performed untilall of the excess material that was deposited in the well region duringprocess 130 is removed and the section 10 of the rotatable shaft 20 isreturned to its original or desired shape. In some aspects, the sectionis polished after the grinding process. Once process 150 is complete,the repair process 100 is also complete and the section 10 of therotatable shaft 20 is considered repaired and ready for use. It shouldbe noted that process 140 may be implemented after process 150 as well.

FIG. 5 is a graphical representation of the disclosed process 100 ofrepairing the section 10 of the rotatable shaft 20. As shown in FIG. 5,500 represents the section 10 of the rotatable shaft 20 that is worn andin need of repair. As shown in 500, there are slight indentations orscuff marks imparted to the outer surface of the section 10. Furthershown in FIG. 5, 502 represents the section 10 of the rotatable shaft 20after process 110 (preparing a well region 50) and prior to process 130(depositing material into the well region 50). As shown in 502, theindentations and scuff marks are no longer present in the section 10 andthe well region 50 has been prepared. As further shown in FIG. 5, 504represents the section 10 of the rotatable shaft 20 after process 130(depositing material into the well region 50) and prior to process 150(displacing a portion of the deposited material). As shown in 504, thewell region 50 has been filled with the deposited material. Next, 506represents the section 10 of the rotatable shaft 20 after process 150(displacing a portion of the deposited material). As shown in 506, theprofile of the section 10 has been reformed and the section 10 is nowfully repaired and the rotatable shaft 20 is ready to be returned toservice.

FIG. 6 is a combustion engine having components that may be repairedutilizing the disclosed process. Referring to FIG. 5, an internalcombustion engine 601 includes one or more shafts that may be repairedaccording to an aspect of the disclosure. The internal combustion engine601 may include an engine block 610 and a turbocharger system 612. Theengine block 610 may include a crankcase within which a crankshaft maybe supported. The crankshaft may be connected to pistons (not shown),which may be movable within respective cylinders during operation of theengine. The engine block 610 may further include a camshaft (not shown)having lobes arranged thereon for valve actuation or the like. Theturbocharger system 612 may include at least one turbocharger havingcomponents that rotate about a shaft. The internal combustion engine 601may further include a pump associated with the cooling system. Thecooling system may include a water pump or coolant pump that may includea shaft. The internal combustion engine 601 may further include alubrication system that may include a lubrication pump or oil pumphaving a shaft. The internal combustion engine 601 may further include ahydraulic pump to provide a source of pressurized hydraulic fluid. Thehydraulic pump may include a shaft. The internal combustion engine mayfurther include a starter motor having a shaft. The internal combustionengine 601 may further include a fuel pump. The fuel pump may havecomponents rotating about a shaft. The internal combustion engine 601may further include components that include at least one shaft that maybe repaired according to an aspect of the disclosure including atransmission, drive train, alternator, auxiliary system and the like.

INDUSTRIAL APPLICABILITY

The disclosure may find applicability in repairing sections 10 of a widerange of rotatable shafts 20. The process may be utilized, for example,in any engine or machine that performs some type of operation associatedwith industry such as mining, construction, farming transportation, orany other industry known in the art.

The process disclosed herein may be used in applications such as motorvehicles, machines, locomotives, marine engines, electrical powergenerators, small mechanical engines, work implements, pumps, etc. Therotatable shaft 20 may be used as a component for a turbine, aturbocharger, a starter, a motor, an alternator, a water pump, ahydraulic pump, a fuel pump, a coolant pump, an oil pump, atransmission, an auxiliary system for a vehicle, and a drivetrain. Forexample, the section 10 of the rotatable shaft 20 may be a lobe, ajournal or a bearing configured on a rotatable shaft 20 for a camshaft,a crankshaft, a water pump shaft, a fuel pump shaft, a coolant pumpshaft, etc.

The disclosed repair process may lead to more efficiently operatingmachines and engines because of the quality of the repair that isachieved. If the section 10 is repaired and the original shape andprofile is restored then the rotatable shaft 20 will be able to operatein a more efficient manner, ultimately resulting in an increaseoperational savings. The disclosed repair process may also be useful toprolong the life of various rotatable shafts 20 as well as prolongingthe life of the machines and engines that use the repaired rotatableshafts 20. As a result, the disclosed repair process may lead toconcomitant savings in part costs as well as labor. The process may alsoresult in reducing scrap and therefore, presenting a greener solution torotatable shaft 20 repair.

We claim:
 1. A process of repairing a section of a rotatable shaft,wherein the section includes a surface portion having a surface parallelto an axis of rotation of the rotatable shaft, the section includesaxial ends perpendicular to the axis of rotation of the rotatable shaft,the process comprising: (a) preparing a well region extending over aperimeter of the section and extending downward in the surface portion,the well region having a bottom portion that is substantially parallelto the axis of rotation and includes opposing sidewalls, wherein eachsidewall extends proximate to the axial ends of the section and directlyadjoins a remaining portion of the surface portion; (b) depositingmaterial into the well region to fill the well region using a weldingprocess; and (c) displacing a portion of the material that was depositedin the well region.
 2. The process of claim 1, wherein the section isone of the following: a lobe or a journal.
 3. The process of claim 2,wherein the rotatable shaft is a camshaft.
 4. The process of claim 1,wherein the preparing includes forming fillets between the bottomportion and the sidewalls.
 5. The process of claim 1, wherein thepreparing utilizes a milling process.
 6. The process of claim 5, whereinthe preparing includes at least one of the following: milling with a keyslot cutter or milling with a ball nose end mill.
 7. The process ofclaim 1, wherein the depositing includes depositing using Laser Beam(LB) Welding.
 8. The process of claim 7, further comprising providingargon gas during the depositing.
 9. The process of claim 1, wherein thedepositing includes depositing with at least one of the following:Plasma Transfer Arc (PTA) Welding, Electron Beam (EB) Welding, MetalInert Gas (MIG) Welding or Tungsten Inert Gas (TIG) Welding.
 10. Theprocess of claim 1, wherein the depositing includes providing one of thefollowing gases proximate to the welding process: argon, carbon dioxideor helium.
 11. The process of claim 1, wherein the displacing includesdisplacing utilizing at least one of the following: a grinding processor a machining process.
 12. The process of claim 1, wherein the materialdeposited is steel.
 13. The process of claim 1, wherein the depositingincludes depositing a powder material.
 14. The process of claim 1,wherein the depositing includes depositing a wire material.
 15. Theprocess of claim 1, wherein the rotatable shaft is a component of one ofthe following: a turbine, a turbocharger, a starter, a motor, analternator, a water pump, a hydraulic pump, a fuel pump, a coolant pump,an oil pump, a transmission, an auxiliary system for a vehicle, or adrivetrain.
 16. The process of claim 1, further comprises pre-weld heattreatment of the section after the preparing and prior to thedepositing.
 17. The process of claim 1, further comprises post-weld heattreatment of the section after the depositing and prior to thedisplacing.
 18. The process of claim 1, wherein the section extendseccentrically from the rotatable shaft.
 19. A process of repairing asection of a rotatable shaft, wherein the section extends eccentricallyfrom the rotatable shaft and includes a surface portion having a surfaceparallel to an axis of rotation of the rotatable shaft, the sectionincludes axial ends perpendicular to the axis of rotation of therotatable shaft, the process comprising: (a) milling a well regionextending over a perimeter of the section and extending downward in thesurface portion, the well region having a bottom portion that issubstantially parallel to the axis of rotation, and opposing sidewalls,wherein each sidewall extends proximate to the axial ends of the sectionand directly adjoins a remaining portion of the surface portion; (b)depositing material into the well region to fill the well region byusing laser beam welding; and (c) grinding a portion of the materialthat was deposited in the well region.
 20. The process of claim 19,wherein the preparing includes forming fillets between the bottomportion and opposing sidewalls and the depositing includes at least oneof the following: depositing a powder material or a wire material.